Method and apparatus for beam recovery of single/multi-beam pair link (bpl) in multi-beam based system

ABSTRACT

A communication method and system for converging a fifth generation (5G) communication system for supporting higher data rates beyond a fourth generation (4G) system with a technology for Internet of things (IoT) are disclosed. The communication method and system may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. A method of a terminal for selecting a candidate beam in a wireless communication system is disclosed. The method includes receiving information on a reference signal from a base station, measuring a plurality beams based on the information on the reference signal, and determining at least one candidate beam among the plurality beams, the candidate beam comprising a beam quality above a threshold.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/934,570 filed on Mar. 23, 2018, which is based on and claims priorityunder 35 U.S.C. § 119 to Korean Patent Application No. 10-2017-0037145filed on Mar. 23, 2017, Korean Patent Application No. 10-2017-0056937filed on May 4, 2017, and of a Korean Patent Application No.10-2017-0075722 filed on Jun. 15, 2017 in the Korean IntellectualProperty Office, the disclosures of which are herein incorporated byreference in their entirety.

BACKGROUND 1. Field

The disclosure relates to a procedure of a base station and a terminalfor a beam recovery when a single/multi-beam pair link (BPL) fortransmission or reception on a control channel is monitored in abeamforming system.

2. Description of Related Art

To meet the demand for wireless data traffic having increased sincedeployment of fourth generation (4G) communication systems, efforts havebeen made to develop an improved fifth generation (5G) or pre-5Gcommunication system. Therefore, the 5G or pre-5G communication systemis also called a ‘beyond 4G network’ or a ‘post long term evolution(LTE) System’. The 5G wireless communication system is considered to beimplemented not only in lower frequency bands but also in higherfrequency (mmWave) bands, e.g., 10 GHz to 100 GHz bands, so as toaccomplish higher data rates. To mitigate propagation loss of the radiowaves and increase the transmission distance, the beamforming, massivemultiple-input multiple-output (MIMO), full dimensional MIMO (FD-MIMO),array antenna, an analog beam forming, and large scale antennatechniques are being considered in the design of the 5G wirelesscommunication system. In addition, in 5G communication systems,development for system network improvement is under way based onadvanced small cells, cloud radio access networks (RANs), ultra-densenetworks, device-to-device (D2D) communication, wireless backhaul,moving network, cooperative communication, coordinated multi-points(CoMP), reception-end interference cancellation and the like. In the 5Gsystem, hybrid frequency shift keying (FSK) and quadrature amplitudemodulation (QAM) (FQAM) and sliding window superposition coding (SWSC)as an advanced coding modulation (ACM), filter bank multi carrier(FBMC), non-orthogonal multiple access (NOMA), and sparse code multipleaccess (SCMA) as an advanced access technology have been developed.

The Internet, which is a human centered connectivity network wherehumans generate and consume information, is now evolving to the Internetof things (IoT) where distributed entities, such as things, exchange andprocess information without human intervention. The Internet ofeverything (IoE), which is a combination of the IoT technology and thebig data processing technology through connection with a cloud server,has emerged. As technology elements, such as “sensing technology”,“wired/wireless communication and network infrastructure”, “serviceinterface technology”, and “Security technology” have been demanded forIoT implementation, a sensor network, a machine-to-machine (M2M)communication, machine type communication (MTC), and so forth have beenrecently researched. Such an IoT environment may provide intelligentInternet technology services that create a new value to human life bycollecting and analyzing data generated among connected things. IoT maybe applied to a variety of fields including smart home, smart building,smart city, smart car or connected cars, smart grid, health care, smartappliances and advanced medical services through convergence andcombination between existing information technology (IT) and variousindustrial applications.

In line with this, various attempts have been made to apply 5Gcommunication systems to IoT networks. For example, technologies, suchas a sensor network, MTC, and M2M communication may be implemented bybeamforming, MIMO, and array antennas. Application of a cloud RAN as theabove-described big data processing technology may also be considered tobe as an example of convergence between the 5G technology and the IoTtechnology.

Recent developments in LTE and LTE-Advanced have led to active researchinto a technique for operating a single/multi-beam pair link (BPL) in amulti-beam based system. For example, it is necessary to study theoperation of the base station and the terminal for beam recovery in thecase of operating a single/multi-BPL in a multi-beam based system.

The above information is presented as background information only toassist with an understanding of the disclosure. No determination hasbeen made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the disclosure.

SUMMARY

Aspects of the disclosure are to address at least the above-mentionedproblems and/or disadvantages and to provide at least the advantagesdescribed below. Accordingly, an aspect of the disclosure is to providea procedure of a base station and a terminal for a beam recovery when asingle/multi-beam pair link (BPL) for transmission or reception on acontrol channel is monitored.

The beam recovery method according to the embodiment of the presentdisclosure defines a beam recovery operation of a base station and aterminal when a single/multi-BPL for transmission and reception on acontrol channel is monitored in a multi-beam based system.

In accordance with a first aspect of the present disclosure, a method ofa terminal for selecting a candidate beam in a wireless communicationsystem is disclosed. The method includes receiving information on areference signal from a base station, measuring a plurality beams basedon the information on the reference signal, and determining at least onecandidate beam among the plurality beams, the candidate beam comprisinga beam quality above a threshold.

In accordance with a second aspect of the present disclosure, a methodof a base station for selecting a candidate beam in a wirelesscommunication system is disclosed. The method includes identifyingreference signals configuring a resource set for measuring a pluralityof beams beam quality, and transmitting information on the referencesignals resource set to a terminal.

In accordance with a third aspect of the present disclosure, a terminalfor selecting a candidate beam in a wireless communication system isdisclosed. The terminal includes a receiver configured to receive asignal from a base station, and a processor. The processor is configuredto control the receiver to receive information on a reference signalfrom the base station, measure a plurality beams based on theinformation on the reference signal, and determine at least onecandidate beam among the plurality beams, the candidate beam comprisinga beam quality above a threshold.

In accordance with a fourth aspect of the present disclosure, a basestation for selecting a candidate beam in a wireless communicationsystem. The terminal includes a transmitter configured to transmit asignal to a terminal, and a processor configured to identify referencesignals for measuring a plurality of beams, and control the transmitterto transmit information on the reference signals to the terminal.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the disclosure.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document: the terms “include” and “comprise,” aswell as derivatives thereof, mean inclusion without limitation; the term“or,” is inclusive, meaning and/or; the phrases “associated with” and“associated therewith,” as well as derivatives thereof, may mean toinclude, be included within, interconnect with, contain, be containedwithin, connect to or with, couple to or with, be communicable with,cooperate with, interleave, juxtapose, be proximate to, be bound to orwith, have, have a property of, or the like; and the term “controller”means any device, system or part thereof that controls at least oneoperation, such a device may be implemented in hardware, firmware orsoftware, or some combination of at least two of the same. It should benoted that the functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely.

Moreover, various functions described below can be implemented orsupported by one or more computer programs, each of which is formed fromcomputer readable program code and embodied in a computer readablemedium. The terms “application” and “program” refer to one or morecomputer programs, software components, sets of instructions,procedures, functions, objects, classes, instances, related data, or aportion thereof adapted for implementation in a suitable computerreadable program code. The phrase “computer readable program code”includes any type of computer code, including source code, object code,and executable code. The phrase “computer readable medium” includes anytype of medium capable of being accessed by a computer, such as readonly memory (ROM), random access memory (RAM), a hard disk drive, acompact disc (CD), a digital video disc (DVD), or any other type ofmemory. A “non-transitory” computer readable medium excludes wired,wireless, optical, or other communication links that transporttransitory electrical or other signals. A non-transitory computerreadable medium includes media where data can be permanently stored andmedia where data can be stored and later overwritten, such as arewritable optical disc or an erasable memory device.

Definitions for certain words and phrases are provided throughout thispatent document. Those of ordinary skill in the art should understandthat in many, if not most instances, such definitions apply to prior, aswell as future uses of such defined words and phrases

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the disclosure will be more apparent from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 shows a procedure of a base station and a terminal for beamrecovery;

FIG. 2 shows a procedure of a base station and a terminal when arespective sequence dedicated for each RR and SR is allocated to eachterminal and the beam correspondence is satisfied in the basestation/terminal according to an embodiment of the present disclosure;

FIGS. 3 and 4 show procedures of a base station and a terminal when asingle dedicated sequence for RR and SR is allocated to each terminaland the beam correspondence is satisfied in the base station/terminalaccording to embodiments of the present disclosure;

FIG. 5 shows a procedure of a base station and a terminal when thededicated sequence is allocated for the SR but is not allocated for theRR and the beam correspondence is satisfied in the base station/terminalaccording to an embodiment of the present disclosure;

FIG. 6 shows a procedure of a base station and a terminal an embodimentwhen the dedicated sequence is allocated for the RR but is not allocatedfor the SR and the beam correspondence is satisfied in the basestation/terminal according to an embodiment of the present disclosure;

FIG. 7 shows an example of the RR procedure when the beam correspondenceat the base station/terminal is established;

FIG. 8 shows an embodiment when the beam correspondence at the basestation end is not established and the beam management RS for the finebeam association is periodically transmitted;

FIG. 9 shows an example of robust beam management mode selectionaccording to the number of beams that the terminal can simultaneouslyreceive;

FIG. 10 shows an example of robust beam management mode selection andmeasurement metric selection according to the number of beams that theterminal can simultaneously receive;

FIG. 11 shows a measurement metric selection in the case of the robustbeam management mode 2;

FIG. 12 shows an embodiment of the overall beam recovery requestprocedure when the terminal performs the mode 1 and when two controlchannel transmission BPLs are monitored for the robust beam management;

FIG. 13 shows a multi-BPL monitoring setup process between the basestation and the terminal for performing the multi-BPL monitoring afterthe terminal initial access;

FIG. 14 shows an RR process of the B BPL during the A BPL monitoring;

FIG. 15 shows an embodiment of the PRACH-like RR region utilization RRprocess for the B BPL during the A BPL monitoring;

FIG. 16 shows an embodiment of the RR region utilization RR process forthe B BPL during the A BPL monitoring;

FIG. 17 shows an embodiment of the operation of the base station and theterminal operation when terminal-subjective RR is performed;

FIG. 18 shows an embodiment where the terminal performs the mode 1;

FIG. 19 shows an embodiment where the DL/UL between the base station andthe terminal may be made from the response of the base station for theRR by the BPL in which the failure does not occur;

FIG. 20 illustrates a block diagram of a base station according to anembodiment of the disclosure; and

FIG. 21 illustrates a block diagram of a terminal according to anembodiment of the disclosure.

Throughout the drawings, like reference numerals will be understood torefer to like parts, components, and structures.

DETAILED DESCRIPTION

FIGS. 1 through 21, discussed below, and the various embodiments used todescribe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably arranged system or device.

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as examples only.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thedisclosure. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of thedisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of thedisclosure is provided for illustration purpose only and not for thepurpose of limiting the disclosure as defined by the appended claims andtheir equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

By the term “substantially” it is meant that the recited characteristic,parameter, or value need not be achieved exactly, but that deviations orvariations, including for example, tolerances, measurement error,measurement accuracy limitations and other factors known to those ofskill in the art, may occur in amounts that do not preclude the effectthe characteristic was intended to provide.

It is known to those skilled in the art that blocks of a flowchart (orsequence diagram) and a combination of flowcharts may be represented andexecuted by computer program instructions. These computer programinstructions may be loaded on a processor of a general purpose computer,special purpose computer, or programmable data processing equipment.When the loaded program instructions are executed by the processor, theycreate a means for carrying out functions described in the flowchart.Because the computer program instructions may be stored in a computerreadable memory that is usable in a specialized computer or aprogrammable data processing equipment, it is also possible to createarticles of manufacture that carry out functions described in theflowchart. Because the computer program instructions may be loaded on acomputer or a programmable data processing equipment, when executed asprocesses, they may carry out operations of functions described in theflowchart.

A block of a flowchart may correspond to a module, a segment, or a codecontaining one or more executable instructions implementing one or morelogical functions, or may correspond to a part thereof. In some cases,functions described by blocks may be executed in an order different fromthe listed order. For example, two blocks listed in sequence may beexecuted at the same time or executed in reverse order.

In this description, the words “unit”, “module” or the like may refer toa software component or hardware component, such as, for example, afield-programmable gate array (FPGA) or an application-specificintegrated circuit (ASIC) capable of carrying out a function or anoperation. However, a “unit”, or the like, is not limited to hardware orsoftware. A unit, or the like, may be configured so as to reside in anaddressable storage medium or to drive one or more processors. Units, orthe like, may refer to software components, object-oriented softwarecomponents, class components, task components, processes, functions,attributes, procedures, subroutines, program code segments, drivers,firmware, microcode, circuits, data, databases, data structures, tables,arrays or variables. A function provided by a component and unit may bea combination of smaller components and units, and may be combined withothers to compose larger components and units. Components and units maybe configured to drive a device or one or more processors in a securemultimedia card.

In a multi-beam based system, a beam pair link (BPL) for transmission ona downlink (DL) and uplink (UL) control/data channel between a basestation and a terminal can be specified. The BPL may refer to a beampair between the base station and the terminal for a composite beam (orwide beam) or a fine beam (or narrow beam) selected based on a beammanagement reference signal (RS). The BPL used for a control channeltransmission and the BPL used for a data channel transmission in oneterminal may be different from each other. In addition, according to abeam correspondence in the base station and the terminal, thetransmission/reception beam direction of the base station and/or thetransmission/reception beam direction of the terminal for UL and DLcommunication configuring the BPL between the base station and theterminal may be specified differently. In addition, the system maymonitor a plurality of BPLs for control/data channel transmission forrobust beam management. In particular, an operation of a plurality ofBPLs for the control channel makes it possible for a terminal to notlose BPLs which can communicate.

If the single/multi-BPL between the base station and the terminal is notavailable (i.e., a beam failure state), the terminal is in a state inwhich it has lost a beam link capable of communicating with the basestation even if it is synchronized with the network. Therefore, beamrecovery is performed to obtain a new BPL. The terminal may recognize abeam failure. The terminal performs continuous measurement using areference signal (RS) configured through a master information block(MIB)/secondary information block (SIB) (or minimum system information(SI)) or RRC signaling from the base station, thereby finding a beamfailure. For example, when a value measured using the RS drops below apredetermined threshold, the terminal may recognize a failure of thecorresponding BPL (at least DL BPL). The RRC may include cell-specificor UE-specific RRC. The RS for a beam failure detection may becell-specific, UE-specific or UE-group-specific. For example, the beamfailure detection RS may be a synchronization signal. Thesynchronization signal can be associated with composite beams or a widebeam which consists of several narrow beams. In another example, thebeam failure detection RS may be an RS mapped to each of the entire finebeams or narrow beams that the base station uses to cover the entireservice area. The fine beam or the narrow beam refers to the beam usedby the base station for transmission on a control channel and/or a datachannel to the terminal.

FIG. 1 shows a procedure of a base station and a terminal for beamrecovery.

Referring to FIG. 1, the base station transmits information on a beamrecovery configuration to a terminal along with information on aconfiguration for a beam failure detection RS at operation 110. Theinformation on the beam recovery configuration may include parametersfor resource, sequence, and a metric operation. For example, the basestation may transmit, to the terminal, a configuration (e.g.,frequency/time information) for resources capable of performing beamrecovery, the sequence for performing the beam recovery, and theparameters (e.g., threshold) to be able to be used to detect the beamfailure. The sequence for performing beam recovery may be dedicatedlyallocated to the terminal or redundantly allocated to many terminals.

The base station transmits the RS for measuring a beam triggeringcondition to the terminal at operation 120. Thereafter, the base stationand the terminal perform a beam recovery procedure based on i) arecovery request, or ii) a BPL(s) update at operation 130.

Hereinafter, embodiments of operations of a base station and a terminalfor beam recovery in various situations will be described.

Operation of Base Station/Terminal According to Recovery Resource

If there is a changeable alternate BPL after detecting the beam failurefor a specific BPL(s), the terminal may transmit a beam recovery requestto the base station. Since the previously used BPL(s) is no longeravailable, the terminal may not transmit a beam recovery request (RR) onthe UL control channel or the data channel communicating with thepreviously used BPL(s). In a region in which the base station sweepsmulti-beam across all directions of a service area, like a random accesschannel (RACH) resource to which an initial access terminal is allocatedto perform random access (RA), the terminal may perform RR. In thesystem in which the beam correspondence with a base station isestablished, the terminal may transmit an RR message to the base stationbased on the preferred beam information acquired through the beammanagement RS, using the resources for RR in which the correspondingbeam performs the reception. The beam management RS may be the same asor different from the beam failure detection RS.

Case 1) Use of Resource Other than RACH for Recovery: Sharing Resourcesfor Recovery/Scheduling Request (SR)

Resources other than the frequency/time/sequence resources (i.e., RACH)defined for the terminal performing the RA may be used for the beamrecovery. The frequency/time/sequence resources defined for the RR maybe a resource that is also allowed to transmit the SR. The frequency andtime resources are shared for the RR and the SR, but embodiments ofvarious alternatives depending on how to allocate the sequence aredescribed in detail below.

Alt 1. Allocate Respective Sequence Dedicated for RR and SR to EachTerminal (Non-Contention Based Recovery/SR)

A respective sequence dedicated for each RR and SR may be allocated toeach terminal. In this alternative, it is possible to perform RR and SRwithout contention among many users even if all the frequency/timeresources for the RR and the SR are shared.

FIG. 2 shows a procedure of a base station and a terminal when arespective sequence dedicated for each RR and SR is allocated to eachterminal and the beam correspondence is satisfied in the basestation/terminal according to an embodiment of the present disclosure.

Referring to FIG. 2, the base station allocates the dedicate sequencefor the RR and the SR to the terminal through the Msg 4 during the RAprocess at the terminal initial connection or through the UE-specificRRC signaling at operation 210. Thereafter, the base station transmitsinformation on the resource configuration necessary for the RR and theSR through the RRC signaling at operation 220.

Thereafter, the terminal may transmit RR in the RR/SR resource using theallocated RR sequence at operation 230. The base station receiving therequest may transmit UL grant at operation 240. At this time, it ispossible to trigger reporting on the preferred BPL information that theterminal updates through the UL grant. In addition, the base station mayindicate the number of preferred BPLs to be reported to the terminal.Thereafter, the terminal may report the information on the BPL(s) to beupdated through uplink control information (UCI) or media accesscontrol-control element (MAC-CE) at operation 250. This information mayinclude a beam (or BPL) ID, a port number for the beam management RS,information on reference signal received power (RSRP) for thecorresponding beam (or BPL), and so on. Thereafter, the base stationtransmits the confirmation information for the newly designated BPL(s)at operation 260. If the newly designated BPL(s) is recognized, from thepoint, the base station and the terminal start to communicate using thenewly designated BPL(s) instead of the existing BPL(s) establishedbetween the base station and the terminal. If the RR resource and eachBPL are associated (that is, if the preferred BPL may be determinedaccording to whether the terminal transmits the RR using which location(e.g., OFDM symbol) of the RR resources), or if the base stationoperates only the single BPL for the terminal, transmitting the UL grantby the base station and reporting of the information on the BPL (s) tobe updated by the terminal of FIG. 2 may be omitted.

Alternatively, the terminal may transmit the SR in the RR/SR resourcesusing the allocated SR sequence at operation 230 a. The base stationreceiving the SR transmits the UL grant to the corresponding terminal atoperation 240 a. The terminal may transmit a buffer status report (BSR)through the MAC-CE or transmit data if the amount of data is very smallat operation 250 a.

This embodiment may be applied to a case where the same sequence isallocated to the terminal for the SR and RR and dedicated frequency/timeresources to be used for transmission of the SR and RR are separatelydivided and allocated within an interval pre-defined to be used for theSR and RR. At this time, the base station will allocate the dedicatedfrequency/time resources instead of transmitting information on theallocation of the dedicated sequence to the terminal.

Alt 2. Allocate Single Sequence Dedicated for and SR to Each Terminal(Non-Contention Based Recovery/SR)

The system may allocate a common dedicated sequence for the RR and theSR to each terminal. In this alternative, since the base stationreceiving the common dedicated sequence for the RR/SR from the terminaldoes not clearly know whether the intention of the terminal correspondsto the RR or the SR, the terminal needs to clarify the intention. FIGS.3 and 4 show procedures of a base station and a terminal when a singlededicated sequence for RR and SR is allocated to each terminal and thebeam correspondence is satisfied in the base station/terminal accordingto embodiments of the present disclosure.

Referring to FIGS. 3 and 4, the base station allocates the singlesequence for the RR and the SR to the terminal through the Msg 4 duringthe RA process at the terminal initial connection or through theUE-specific RRC signaling at operations 310 and 410. Thereafter, thebase station transmits information on the resource configurationnecessary for the RR and the SR to the terminal through the RRCsignaling at operations 320 and 420. Thereafter, when the terminaldesires to perform the RR or the SR, the terminal transmits the RR orthe SR in the resources for the RRs and SR using the allocated sequenceat operations 330 and 430. Thereafter, the base station transmits the ULgrant to the terminal at operation 340 and 430. Referring to FIG. 3, theterminal to perform the RR may transmit the information on the newBPL(s) using the MAC-CE, and the terminal to perform the SR may transmitBSR or data at operation 350. As described above, the information on thenew BPL(s) may include a beam (or BPL) ID, a port number for the beammanagement RS, information on RSRP for the corresponding beam (or BPL),and so on. Since the BPL(s) information or the BSR will be formatted anddivided, the base station may clearly know the purpose of the requestsequence through the MAC-CE of the terminal. When it is determined thatthe terminal transmitted the sequence for the RR through the MAC-CE atoperation 330, the base station may confirm the information on theupdated BPL(s) at operation 360, whereas when it is determined that theterminal transmitted the sequence for the SR through the MAC-CE atoperation 330, the base station may allocate the resources for theterminal to transmit data at operation 360. Referring to FIG. 4, theterminal to perform the RR may transmit BPL(s) information, or the BSRalong with BPL(s) information through a UCI at operation 450. If theterminal transmits only BPL(s) information, the base station maydetermine that the terminal transmitted the sequence for the RR. If theterminal transmits the BSR or the BPL(s) information along with the BSR,it may determine that the terminal transmitted the sequence for the SR.Similar to the embodiment of FIG. 3, the base station may confirm theinformation on the updated BPL(s) or allocate the resources for theterminal to transmit data according to the determining of whether theterminal transmitted the sequence for the RR or SR at operation 460.

This embodiment may be applied to a case where the same sequence isallocated to the terminal for the SR and RR and the same dedicatefrequency/time resources to be used for transmission of the SR and RRare allocated within an interval pre-defined to be used for the SR andRR. At this time, the base station will allocate the dedicatefrequency/time resources instead of allocating the dedicate sequence tothe terminal.

Alt 3. Allocate Dedicated Sequence for Either RR or SR to Each TerminalAlt 3-1. Allocate Dedicated Sequence for SR+not Allocate DedicatedSequence for RR (Contention Based Recovery)

The system may allocate the dedicated sequence to each terminal for theSR and not allocate the dedicated sequence for recovery. In thisalternative, the sequences available for the RR and SR should be dividedinto two sets, i.e., a set for the RR or a set for the SR. That is, onesequence is included only in one set of two sets. The SR sequencededicatedly allocated to the terminal is selected from the sequence setfor the SR, and all terminals in the cell may select a sequence atrandom from the sequence set for the RR and use the selected RRsequence. In addition, in this case, even if the frequency/timeresources for the RR and the SR are the same, contention does not occurbetween the terminals for the SR and the RR. FIG. 5 shows a procedure ofa base station and a terminal when the dedicated sequence is allocatedfor the SR but is not allocated for the RR and the beam correspondenceis satisfied in the base station/terminal according to an embodiment ofthe present disclosure.

Referring to FIG. 5, the base station selects and allocates the SRsequence from the sequence set for the SR through the Msg 4 at theterminal initial access or the UE-specific RRC at operation 510. Asdescribed above, the sequence set is divided into the set for the SR andthe set for the RR. Thereafter, the base station transmits informationon the resource configuration necessary for the RR and the SR to theterminal through the RRC signaling at operation 520. Thereafter, theterminal selects a sequence randomly among the sequence set for the RRand performs the RR at operation 530. The base station transmits the ULgrant for the RR at operation 540. The DCI for receiving thecorresponding UL grant is scrambled with a specific radio networktemporary identifier (RNTI). This particular RNTI may be related to theRR sequence used by the terminal. The UL grant may include informationon the number of BPLs. The terminal receiving the UL grant transmits newBPL(s) information to be updated and C-RNTI on a physical uplink sharedchannel (PUSCH) at operation 550. The terminal already has the C-RNTIsince the terminal is connected to the network. Therefore, since it ispossible that there is a user using the same RR sequence and resources,the C-RNTI may be transmitted for performing contention resolution.Thereafter, the base station transmits the BPL(s) confirmationinformation to the terminal along with the contention resolution messageat operation 560.

Alternatively, the terminal may transmit the SR to the base stationusing the sequence allocated for the SR at operation 530 a. For example,the terminal may use MSG1 for transmission of the SR. The base stationreceiving the SR transmits the UL grant to the terminal at operation 540a.

This embodiment may be applied to a case where the same sequence isallocated to the terminal for the SR and RR, and the dedicatefrequency/time resources to be used for the transmission of the SR areseparately allocated within the interval pre-defined for the SR and RR,but the dedicate frequency/time resources to be used for thetransmission of the RR are not allocated and the terminal randomlyselects the resources for the RR to transmit the RR. At this time, thebase station needs to give information on whether the areas for the SRand RR are separately divided in the area initially designated for theSR and RR.

Alt 3-2. Allocate Dedicated Sequence for RR+not Allocate DedicatedSequence for SR (Contention Based SR)

The system may allocate the dedicated sequence to each terminal for theRR and not allocate the dedicated sequence for the SR. In thisalternative, the sequences available for the RR and SR should be dividedinto two sets, i.e., a set for the RR or a set for the SR. That is, onesequence is included only in one set of two sets. The RR sequencededicatedly allocated to the terminal is selected from the sequence setfor the RR, and all terminals in the cell may select a sequence atrandom from the sequence set for the SR and use the selected SRsequence. In addition, in this case, even if the frequency/timeresources for the RR and the SR are the same, contention does not occurbetween the terminals for the SR and the RR. FIG. 6 shows a procedure ofa base station and a terminal when the dedicated sequence is allocatedfor the RR but is not allocated for the SR and the beam correspondenceis satisfied in the base station/terminal according to an embodiment ofthe present disclosure.

Referring to FIG. 6, the base station selects and allocates the RRsequence from the sequence set for the RR through the Msg 4 at theterminal initial access or the UE-specific RRC at operation 610. Asdescribed above, the sequence set is divided into the set for the SR andthe set for the RR. Thereafter, the base station transmits informationon the resource configuration necessary for the RR and the SR to theterminal through the RRC signaling at operation 620. Thereafter, theterminal selects a sequence randomly among the sequence set for the SRand performs the SR at operation 630 a. The base station transmits theUL grant for the SR at operation 640 a. The DCI for receiving thecorresponding UL grant is scrambled with a specific RNTI. Thisparticular RNTI may be is related to the SR sequence used by theterminal. The terminal receiving the UL grant transmits BSR informationand C-RNTI on the PUSCH at operation 650 a. The terminal already has theC-RNTI while being connected to the network. Therefore, if there is auser using the same SR sequence at the location in the same SR resource,the C-RNTI is transmitted for the purpose of performing contentionresolution. Thereafter, the base station allocates resources for theterminal to transmit the UL data together with the contention resolutionmessage at operation 660 a.

This embodiment may be applied to a case where the same sequence isallocated to the terminal for the SR and RR, and the dedicatefrequency/time resources to be used for transmission of the RR areseparately allocated within the interval pre-defined for the SR and RR,but the dedicate frequency/time resources to be used for transmission ofthe SR are not allocated and the terminal randomly selects the resourcesfor the SR to transmit the SR. At this time, the base station needs togive information on whether the areas for the SR and RR are separatelydivided in the area initially designated for the SR and RR.

Case 2) When Using RACH Resource for Recovery

In the system, the same frequency/time/sequence resources can be usedfor the RA for the initial access terminals and the RR. In this case,the terminal clarifies whether the terminal requests the RR or theterminal is an initial access terminal through the DCI or the MAC-CE inMsg 3, similar to the embodiment of the Alt 2 (FIGS. 3 and 4) of Case 1.

Operation of Base Station/Terminal According to Beam Failure DetectionRS

In order to select the BPL between the base station and the terminal,the terminal may select a rough beam (composite beam or wide beam) usingthe synchronization signal, or select a fine beam based on the RScorresponding to the fine beam or narrow beam used when the base stationperforms transmission on the data channel and the control channel. Thismay be changed according to the operation of the base station.

Case 1) When Periodic DL Beam Management RS (Cell-Specific orUE-Specific) Capable of Fine Beam Association is Transmitted

If the DL beam management RS capable of selecting the fine beam isperiodically transmitted, the terminal may monitor the BPL(s) which canbe changed through the RS when the beam failure continuously occurs. Ifthe beam correspondence is established in the base station/terminal, theoperation of the base station/terminal can be performed such as thealternatives above-mentioned in the “operation of the basestation/terminal based on the recovery resource”.

Case 2) When Periodic DL Beam Management RS (Cell-Specific orUE-Specific) Capable of Only Rough Beam Association is Transmitted, orwhen Periodic Beam Management RS is not Transmitted

If the DL beam management RS capable of selecting the fine beam is notperiodically transmitted or only the DL beam management RS capable ofthe rough beam association is periodically transmitted (for example,synchronization signal), the operation of the base station and theterminal different from the above-mentioned schemes should be defined.As the BPL for the control and/or data transmission established by theexisting base station and terminal should be updated by the beamrecovery request process, the channel state information-reference signal(CSI-RS) should be transmitted so that the preferred BPL(s) of theterminal in the beam recovery request process may be selected andreported. The BPL(s) may include the information on the fine beam.

FIG. 7 shows an example of the RR procedure when the beam correspondenceat the base station/terminal is established.

Referring to FIG. 7, the base station selects and allocates the SRsequence from the sequence set for the SR through the Msg 4 at theterminal initial access or the UE-specific RRC at operation 710. Asdescribed above, the sequence set is divided into the set for the SR andthe set for the RR. Thereafter, the base station transmits informationon the resource configuration necessary for the RR and the SR to theterminal through the RRC signaling at operation 720. Compared with theRR-related base station-terminal operation of FIG. 5, when the basestation receives the RR from the terminal at operation 730, the basestation can activate the CSI-RS transmission configured through the RRCwhen transmitting the UL grant at operation 740. The UL grant mayinclude information on the number of BPLs. Upon performing the RR, theterminal may select the location in the resources for the RRcorresponding to the BPL for the preferred rough beam obtained by usingthe synchronization signal or the like, which the base station transmitswith the composite beam, such that the base station may find the roughbeam that the terminal prefers based on the location within the resourcefor the RR in which the terminal performs the RR. Therefore, thetransmission beam of the base station which is transmitted for the finebeam selection of the terminal in the corresponding CSI-RS resource maybe the narrow beams configuring the corresponding rough beam. The basestation transmits the activated (aperiodic) CSI-RS at operation 750after the UL grant, and the terminal may select the port number(s) ofthe preferred CSI-RS through a PUSCH and reports the BPL(s) informationincluding the selected port number(s), thereby updating the BPL in whichthe beam failure occurs at operation 760. In this case, FIG. 7illustrates an embodiment of the system for operating thecontention-based RR as shown in FIG. 5, wherein the terminal transmitsthe C-RNTI along with the selected BPL(s) information to help the basestation perform the contention resolution at operation 770. The basestation may transmit the beam confirmation information to the terminalalong with the contention resolution message. FIG. 7 shows an example.In addition to the embodiment shown in FIG. 7, when the base station canfind that the terminal transmitted the RR based on the sequencetransmitted in the RR resource, the base station may include theoperation of activating the CSI-RS when transmitting the UL grant afterreceiving the RR sequence.

In another embodiment of the present disclosure, the base station havingreceived the RR does not include the CSI-RS activation information whentransmitting the UL grant, and after the terminal reports the preferredrough beam through the DCI or the MAC-CE, the base station may activatethe CSI-RS via the DCI (transmitted in the rough beam or the compositebeam) and then the terminal selects a new BPL (with fine-beam) based onthe CSI-RS.

Operation of Base Station/Terminal when Beam Correspondence is notEstablished at Base Station End

The fact that the beam correspondence is not established at the basestation end means that the beam direction used for DL signaltransmission at the base station may not be the same as the beamdirection used for the UL signal reception. In this case, the terminalcan select the preferred DL transmission beam of the base stationthrough the RS for the beam management. The RS for the beam managementmay refer to the synchronization signal transmitted through thecomposite beam or the RS capable of the fine beam association. However,since the terminal may not know through which reception beam the basestation successfully receives the corresponding RR is successfullyreceived when the RR is performed, the RR sequence should be transmittedfrom the resource location for the RR corresponding to the receptionbeam of the base station in all directions. If the terminal transmitsthe preferred DL transmission beam information of the base station whentransmitting the RR, the base station may use the DL transmission beamin the corresponding direction when transmitting the response to the RRof the terminal later. There are two schemes of transmitting thepreferred DL transmission beam information of the base station when theterminal transmits the RR. The first scheme includes the correspondinginformation in the sequence used at the time of the RR. The first schememay be used when the sequence for the RR and SR or the time/frequencyresources for the RR and the SR are separated. Alternatively, the firstscheme can be available even when the sequence or the time/frequencyresources for the RA and the RR is shared. The second scheme separatesthe resources according to the DL transmission beam of the base stationwithin the resource for the RR. If the resource is configured asdescribed above, the terminal may transmit the RR at the locationcorresponding to the preferred DL transmission beam of the base stationwithin the resource for the RR to transmit the corresponding informationto the base station.

As described above, when the beam correspondence is not established atthe base station end, the transmission/reception beam directions forcommunicating with the terminal may be different. Therefore, the DLtransmission beam for communicating with the specific terminal may befound when the terminal transmits the RR, but the process of finding thebeam for receiving the corresponding information when the terminaltransmits the UL information is required. Accordingly, the terminal isinstructed to transmit the SRS during the beam recovery request process,and therefore a process of selecting, by the base station, the receptionbeam to be used at the time of receiving the UL signal that thecorresponding terminal transmits is required.

FIG. 8 shows an embodiment when the beam correspondence at the basestation end is not established and the beam management RS for the finebeam association is periodically transmitted.

Referring to FIG. 8, the base station may inform the terminal whetherthe beam correspondence is established at the base station end through aminimum SI at operation 810. Thereafter, the base station allocates thesequence for the RR or the SR to the terminal through the Msg 4 duringthe RA process at the terminal initial connection or through theUE-specific RRC signaling at operation 820, and transmits information onthe resource configuration necessary for the RR and the SR to theterminal through the (UE-specific) RRC signaling at operation 830. Ifthe beam correspondence is not established, the base station receivingthe RR at operation 840 may include the information on whether the basestation DL transmission beam information that the terminal prefers iscorrect when the base station transmits the UL grant at operation 850 inorder to select the beam for receiving the corresponding informationwhen the terminal transmits the UL information, and may request the SRStransmission to the terminal. The UL grant may include information onthe number of BPLs. After the terminal receiving the UL grant canconfirm that the DL transmission beam included in the UL grant iscorrect through the UCI at operation 860, the terminal transmits the(aperiodic) SRS that the base station requests to select the beam forreceiving the corresponding information when the terminal transmits theUL information of the terminal at operation 870. The base station maytransmit the BPL(s) confirmation information to the terminal atoperation 880.

FIG. 8 shows an example. In addition to the embodiment shown in FIG. 8,when the base station can find that the terminal transmitted the RRbased on the sequence transmitted in the RR resource, the base stationmay include the operation of instructing the terminal to transmit theSRS when transmitting the UL grant after receiving the RR sequence.

Base Station/Terminal Operation in Multi-BPL Operation for ControlChannel Transmission

For the robust communication, it is possible to consider the system formonitoring the plurality of BPLs for transmitting the control channelbetween the base station and the terminal. This robust beam managementcan be applied to all terminals in the cell or only to some terminals.

Multi-Physical Downlink Control Channel (PDCCH) Monitoring Mode andMeasurement Metric Selection

The robust beam management scheme of the base station can be selectedaccording to the number of beams that the terminal can simultaneouslyreceive.

FIG. 9 shows an example of robust beam management mode selectionaccording to the number of beams that the terminal can simultaneouslyreceive.

As shown in FIG. 9, if the terminal may receive only one beam at a timeaccording to the information transmitted through capability negotiation(910) after the RA, the base station can select and allocate the robustbeam management mode 0 or 1 to the terminal (920). Alternatively, if theterminal is capable of receiving multi-beam at a time, the base stationmay select and allocate one of the robust beam management modes 0/1/2(930, 940, 950). In the robust beam management mode, the mode 0 is amode in which the terminal receives one control beam at a time among themulti-BPLs, the mode 1 is a mode in which the terminal receives one beamat a time among the multi-BPLs but a candidate BPL which is beingmonitored is monitored at different frequencies, and the mode 2 is amode in which the terminal receives beams corresponding to multi-BPLs ata time. In the mode 1, a plurality of monitoring BPLs is received atdifferent OFDM symbols, and in the mode 2, the plurality of monitoringBPLs is received at one OFDM symbol. The terminal needs an operation ofperforming measurement based on a specific RS to distinguish the beamfailure of the BPLs while the BPL associated with the robust beammanagement is monitored. In this case, the RS for the terminal todistinguish the beam failure may be the RS which corresponds to thesynchronization signal (composite beam) including the beam through whichthe base station performs transmission on the control channel or the BPLassociated with the beam through which the base station performstransmission on the control channel. In particular, in the case of themode 2 (950), the scheme of calculating the above-described RS may bevariously defined in order to distinguish the beam failure when theterminal performs the measurement, and this calculation scheme is calleda measurement metric. For example, in the case of the mode 2 (950),measurement metric 0 or 2 may be selected (960).

FIG. 10 shows an example of robust beam management mode selection andmeasurement metric selection according to the number of beams that theterminal can simultaneously receive.

Referring to FIG. 10, if the terminal may receive only one beam at atime according to the information transmitted through capabilitynegotiation (1010) after the RA, the base station can select andallocate the robust beam management mode 1 to the terminal (1020).Alternatively, if the terminal is capable of receiving multi-beam at atime, the base station may select and allocate one of the robust beammanagement modes 1 or 2 (1030). Based on whether mode 1 or 2 is selected(1040), the measurement metric is determined (1050, 1060). For example,the measurement metric 0 is configured for the terminal which drives therobust beam measurement mode 1 (1050), whereas the base station maydesignate the measurement metric 0 or 1 for the terminal which drivesthe robust beam measurement mode 2 (1060). The measurement metric 0means performing the quality measurement in the single RS for each BPL(1070), and the measurement metric 1 means performing the qualitymeasurement on the plurality of BPLs in the single RS (1080). Accordingto another embodiment, the system can support only modes 1 and 2 exceptfor mode 0. At this time, the mode 1 and 2 may be selected according tothe terminal capability.

FIG. 11 shows a measurement metric selection in the case of the robustbeam management mode 2.

Referring to FIG. 11, the quality measurement is performed based onwhether the measurement metric is 0 or 1. Specifically, in the case ofmeasurement metric 1, the quality measurement is performed in single RSfor each BPL (1170). In the case of measurement metric 2, the qualitymeasurement is performed on multi-BPL in single RS.

Beam Failure Recovery Request (RR) Channel

When performing the single/multi-BPL transmissions for the controlchannel in the system (not limited to multi-BPL), the PRACH-like channeland the PUCCH received by allowing the base station to sweep in alldirections may be used to receive the RR for the BPL upon the occurrenceof the failure. What channel the base station will use may be configuredin the terminal by higher layer signaling. In other words, only thePRACH-like channel may be utilized or both channels may be utilized.

Beam Failure Detection RS

If the system performs the single/multi-BPL transmission for the controlchannel (not limited to the multi-BPL), the synchronization signal (SS)block and/or CSI-RS or the like may be used to detect the failure of thespecific BPL. In particular, to detect the failure of the specific BPL,the terminal measures the demodulation reference signal (DMRS) of thePDCCH transmitted in the specific BPL and the quasi-co-located (QCLed)SS block and/or CSI-RS. A signal-to-interference-plus-noise ratio(SINR)-like metric or L1-RSRP can be used as the measurement metric.That is, if the SINR-like metric or the L1-RSRP for the specific BPLamong the BPLs that the terminal is monitoring drops below apredetermined threshold, it can be defined that the failure of thecorresponding BPL occurs. It is possible to be specified in the standardthat the terminal detects beam failure based on which RS among the SSblock, the CSI-RS or the SS block+CSI-RS, or the base station mayconfigure it through the higher layer signaling. The configuration ofthe base station may select one of the three methods described above, ormay select one of some methods (e.g., SS block or CSI-RS).

In particular, if the base station configures the beam failure detectionRS, the threshold for beam failure detection may be different. Forexample, the beam failure of the specific monitoring BPL referenced bySS block is detected when the L1-RSRP of the monitoring BPL is smallerthan the Ta, and the beam failure of the specific monitoring BPLreferenced by CSI-RS may be detected when the L1-RSRP of the monitoringBPL is smaller than Tb. Also, when considering both of the SS block andthe CSI-RS, the beam failure of the specific monitoring BPL may bedetected when the L1-RSRP is smaller than Tc. In this case, the valuesTa, Tb, and Tc may be specified in the standard or the base station mayconfigure the values Ta, Tb, and Tc through higher layer signaling.

New Candidate Beam Identification RS

If the system performs the single/multi-BPL transmission for the controlchannel (not limited to the multi-BPL), the SS block and/or CSI-RS orthe like may be used to select the alternative BPL of the specificfailure occurrence BPL(s). New candidate beam identification RS forfinding the alternative BPL of the failure occurrence BPL(s) may bedesignated in the standard or may be configured in the base station. Theterminal may select the alternative BPL of the failure occurrence BPL(s)by the L1-RSRP measurement of the new candidate beam identification RS.Whether to use the SS block, the CSI-RS, or both of the SS-block and theCSI-RS as the new candidate beam identification RS may be designated inthe standard or may be configured in the base station through the higherlayer signaling. The configuration of the base station may select one ofthe three methods described above, or may select one of some methods(e.g., SS block or CSI-RS).

In particular, if the base station is configured to use both RSs, thebase station may issue an instruction to perform a search by allocatingpriority to which of the two RSs. For example, if the base stationallocates the priority for the use of the CSI-RS, the terminal mayperform the SS block review after reviewing CSI-RS for new beamidentification.

The threshold for the new beam identification may be changed dependingon which RS is used for the new beam identification. For example, if thenew beam identification is performed based on the SS block, a newcandidate beam can be selected when the L1-RSRP of the specific BPL isgreater than Ta, if the new beam identification is performed based onthe CSI-RS, the candidate beam may be selected when the L1-RSRP isgreater than Tb, if both of the SS block and the CSI-RS are used toperform the new beam identification, the terminal may use differentthreshold values depending on which RS is used for performing the newbeam identification (i.e., finding a new beam) (e.g., Tc based on the SSblock, Td based on the CSI-RS). That is, if a new beam is preferentiallysearched in the CSI-RS configured in the terminal, the new candidatebeam may be selected when the L1-RSRP of the specific BPL is greaterthan Tc, but if the new beam is not searched based on the CSI-RS, the SSblock may be searched. At this time, if the L1-RSRP of the specific BPLis greater than Td, the new candidate beam is selected. The values Ta,Tb, Tc, and Td may be specified in the standard or the base station mayconfigure the values Ta, Tb, Tc, and Td through higher layer signaling.

Period of Beam Failure Detection RS and New Candidate BeamIdentification RS

When the system performs the single/multi-BPL transmission for thecontrol channel (not limited to multi-BPL), as described above, the SSblock, the CSI-RS, or the SS block and the CSI-RS may be used as thebeam failure detection RS and/or the new candidate beam identificationRS. When the SS block and the CSI-RS are used for the beam failuredetection and/or the new candidate beam identification, the base stationmay configure each period through the higher layer signaling. Forexample, if the SS block is used for the new candidate beamidentification, the base station may configure the period of the SSblock for new candidate beam identification to be 20 milliseconds (ms).This configuration value may also be interpreted as the period of the SSblock for the beam management. In another embodiment, when the SS blockis used for the beam failure detection and new candidate beamidentification, the SS block periods for the beam failure detection andthe new candidate beam identification may be set to be one configuration(common period) or to different values. In another embodiment, when theCSI-RS is used for the beam failure detection and new candidate beamidentification, the CSI-RSs periods for the beam failure detection andthe new candidate beam identification may be set to be one configuration(common period) or to different values.

In another embodiment, the terminal may assume the SS block period as aspecific value upon the beam failure detection and/or the new candidatebeam identification. For example, if the SS block is used for the newcandidate beam identification, the terminal may assume a 20 ms periodwhen receiving the SS block for the new candidate beam identification.

Beam Failure RR Triggering Condition

In the system where the multi-BPL is monitored, performing the beam RRby the terminal is triggered if one of the following conditions issatisfied.

1) When the failure occurs for all the multi-BPLs that the terminal ismonitoring and at least one alternative beam (i.e., new candidate beam)is found

2) A failure occurs for some of the multi-BPLs that the terminal ismonitoring. One or more alternative beams are not necessarily found. Inparticular, at this time, the beam, in which the failure does not occur,among the monitoring BPLs are not considered as an “alternative beam”for the failure occurrence beam.

3) A failure occurs for some of the multi-BPLs that the terminal ismonitoring, and one or more alternative beam is found for the BPL inwhich at least one failure occurs. In particular, at this time, the BPL,in which the failure does not occur, among the monitoring BPLs areconsidered as an “alternative beam” for the failure occurrence beam.

In particular, the conditions 2) and 3) are divided according to themeaning of the “alternative beam” defined in the standard, meaning thatthe terminal may report the failure occurrence BPL to the base stationeven when only a part of the entire monitoring BPL fails.

Alternatively, the above-described beam RR performance triggeringcondition may be applied only when the specific channel is used. Forexample, a scheme of performing the beam failure RR using the PRACH-likechannel only when the condition 1) is satisfied, or performing the beamfailure RR using the PUCCH if the condition 2) or the condition 3) issatisfied is possible.

PRACH-Like Recovery Request Resource Association

If the system performs the single/multi-BPL transmission for the controlchannel (not limited to the multi-BPL), the PRACH-like recovery requestresource may be associated with the SS block or the CSI-RS.Alternatively, the PRACH-like recovery request resource may beassociated with the SS block and the CSI-RS. The PRACH-like recoveryrequest resource selected by the terminal is at least associated withthe transmission beam for the base station to transmit a response to therecovery request. That is, the base station may select the transmissionbeam to transmit the response through the resource information in whichthe terminal transmits the recovery request, and the terminal mayreceive a response by a reception beam corresponding to the transmissionbeam. Also, the terminal may transmit the preferred alternative BPLinformation for replacing the failure BPL according to the PRACH-likerecovery request resource in which the terminal performs the recoveryrequest.

Association of PRACH-Like Recovery Request Resource with New CandidateBeam Information

When the system performs the single/multi-BPL transmission for thecontrol channel (not limited to multi-BPL), the resource(time/frequency/sequence) selected by the terminal at the time of the RRis at least to designate the transmission beam for the base station toperform the response to the RR. Alternatively, the resource selected bythe terminal at the time of RR may include the preferred BPL informationfor the terminal to replace the failure occurrence BPL, whiledesignating the transmission beam for the base station to perform theresponse to the RR.

FIG. 12 shows an embodiment of the overall beam recovery requestprocedure when the terminal performs the mode 1 and when two controlchannel transmission BPLs are monitored for the robust beam management.

As described above, there is shown a multi-monitoring BPL setup processbetween the base station and the terminal for performing the multi-BPLmonitoring after the terminal initial access. Based on information onthe number of the concurrent beam reception that the terminal transmitsat operation 1205, the base station transmits the robust beam managementmode and the measurement metric through the UE-specific RRC signaling atoperation 1210. Also, the base station may also inform the terminalabout how many BPLs are monitored for the robust beam management mode.According to this value, the terminal may know how many preferred BPLinformation should be reported. In the case of the mode 1, the basestation may also inform the terminal of the monitoring rule. Forexample, when the two BPLs are monitored, it may be inform how often twoBPLs are changed and used. For example, if BPL A and BPL B are each usedalternately over 8 slots and 2 slots, the DL and UL transmission may bemade in A BPL from a next slot to the eighth slot based on a slot wherethe DCI confirming the multi-BPL is transmitted, and the DL and ULtransmission to the B BPL may be made during the next slot No. 2. Afterthe UE-specific RRC signaling, the base station may activate the CSI-RSand the reporting for the corresponding CSI-RS through the DCI so thatthe terminal may select the preferred multi-BPL at operation 1215. Inthis case, the beam used to transmit the DCI may be the base stationtransmission beam corresponding to the preferred BPL that the terminalreports during the initial access process, or the base stationtransmission beam transmitted by allowing the terminal to select theRACH resource during the initial access process. Thereafter, if theCSI-RS activated by the base station is transmitted at operation 1220,the terminal selects and reports the preferred BPL based on themeasurement performed by the corresponding CSI-RS at operation 1225.Thereafter, the base station carries the ID (or CSI-RS port number) forthe monitoring beams determined based on the terminal reporting and theinformation on the order on the DCI at operation 1230. In this case, thebeam used to transmit the DCI may be the base station transmission beamcorresponding to the preferred BPL that the terminal reports during theinitial access process, or the base station transmission beamtransmitted by allowing the terminal to select the RACH resource duringthe initial access process. Based on this point, the monitoring for afirst (dominant) BPL starts.

If the beam failure of other monitoring BPL(s) is determined in theperiod in which the monitoring is continued in a first BPL and the basestation triggers the quality report of the monitoring BPL through theDCI at operation 1235, the terminal may perform the quality report ofthe monitoring BPL through the UCI or the MAC-CE at operation 1240. Inthis case, when the periodic beam management RS is transmitted, theterminal can feed back the preferred BPL, which can replace the locationof the observed BPL with beam failure. However, if the periodic beammanagement RS is not transmitted or the beam management RS is unsuitablefor selecting the fine beam, then the base station may transmit the DCIthrough the first BPL and activate the CSI-RS and the correspondingreporting to select the new BPL at operation 1245. Through the CSI-RSreception at operation 1250, the terminal reports the new BPLinformation to fill the location of the failure beam at operation 1255.If a new order needs to be re-established between the current first BPLand the newly reported BPL under the base station determination, the DCImay arrange the order and inform the order at operation 1260. If thenext 2nd BPL monitoring timing starts, the monitoring starts in a secondBPL in the updated BPL lists at the second BPL monitoring timing.

If the failure of the first BPL is detected during the monitoring of theBPL other than the BPL having the first priority or during theconnection of the first BPL and if the base station triggers the qualityreport by the DCI transmitted in the second BPL at operation 1265, theterminal may transmit the quality report of the BPL, which ismonitoring, through the UCI or the MAC-CE at operation 1270. In thiscase, when the periodic beam management RS is transmitted, the terminalcan feed back the preferred BPL, which can replace the location of theobserved BPL with beam failure. However, if the periodic beam managementRS is not transmitted or the beam management RS is unsuitable forselecting the fine beam, then the base station may transmit the DCIthrough the second BPL and activate the CSI-RS and the correspondingreporting to select the new BPL at operations 1280 and 1285. If theterminal notifies the failure of the first BPL through the UCI, the basestation immediately changes the currently connected BPL to the firstBPL. It is possible to start new monitoring on the assumption that thesecond BPL is the first BPL based on the timing at which it confirmsthat the second BPL has been changed to the first BPL through DCI.Alternatively, it is also possible to look at the second BPL for thefirst BPL monitoring period based on the timing at which the second BPLmonitoring starts originally. Through the CSI-RS reception, the terminalreports the new BPL information to fill the location of the failurebeam. If a new order needs to be re-established between the currentfirst BPL and the newly reported BPL under the base stationdetermination, the DCI may arrange the order and inform the order atoperation 1295. If the next 2nd BPL monitoring timing starts, themonitoring starts in the second BPL in the updated BPL list at thesecond BPL monitoring timing.

According to another embodiment, when the failure of the BPL currentlyconnected to the base station is detected, if the terminal may have theopportunity to use the beam recover request resource during themonitoring of the BPL currently connected to the base station (if thebeam recovery request resource is defined during the monitoringinterval), the terminal may notify the failure of the corresponding BPLthrough the RR resource. Thereafter, to fill the location of the failedBPL, a new BP may be reported. Therefore, the base station may confirmthe updated BPL list information to the terminal through the RRC or theMAC-CE or the DCI.

An embodiment of the sub-divided beam recovery request procedure whenthe terminal performs the mode 1 and when two control channeltransmission BPLs are monitored for the robust beam management is shownin FIGS. 13 to 19. In FIGS. 13 to 19, when ordering the failure BPLinformation transmission of the terminal and the monitoring BPL(s) ofthe base station, the information about the ID re-established for themonitoring BPLs other than the ID of the beam associated with the actualCSI-RS or the like may be included.

Multi-Monitoring BPL Setup Between Base Station and Terminal forPerforming Multi-BPL Monitoring

FIG. 13 shows a multi-BPL monitoring setup process between the basestation and the terminal for performing the multi-BPL monitoring afterthe terminal initial access. Based on the concurrent beam receptionnumber information that the terminal transmits, the base stationtransmits the robust beam management mode and the measurement metricthrough the UE-specific RRC signaling at operation 1310. Also, the basestation may also inform the terminal about how many BPLs are monitoredfor the robust beam management mode at operation 1320. According to thisvalue, the terminal may know how many preferred BPL information shouldbe reported. In the case of the mode 1, the base station may also informthe terminal of the monitoring scheme. For example, when the two BPLsare monitored, it may be inform how often two BPLs are changed and used.For example, if BPL A and BPL B are each used alternately over 8 slotsand 2 slots, the DL and UL transmission may be made in A BPL from a nextslot to slot No. 8 based on a slot where the DCI confirming themulti-BPL is transmitted, and the DL and UL transmission may be made inB BPL during the next slot No. 2. After the UE-specific RRC signaling,the base station may activate the CSI-RS and the reporting for thecorresponding CSI-RS through the DCI or the MAC-CE so that the terminalmay select the preferred multi-BPL at operation 1330. In this case, thebeam used to transmit the DCI or the MAC-CE may be the base stationtransmission beam corresponding to the preferred BPL that the terminalreports during the initial access process, or the base stationtransmission beam transmitted by allowing the terminal to select theRACH resource during the initial access process. Thereafter, if theCSI-RS activated by the base station is transmitted at operation 1340,the terminal selects and reports the preferred BPL based on themeasurement performed by the corresponding CSI-RS at operation 1350.Thereafter, the base station carries the ID (or CSI-RS port number) forthe monitoring beams determined based on the terminal reporting and theinformation on the order on the DCI or the MAC-CE at operation 1360. Inthis case, the beam used to transmit the DCI or the MAC-CE may be thebase station transmission beam corresponding to the preferred BPL thatthe terminal reports during the initial access process, or the basestation transmission beam transmitted by allowing the terminal to selectthe RACH resource during the initial access process. Based on thispoint, the monitoring for a first (dominant) BPL starts.

Beam Failure Recovery by Base Station BPL Quality Reporting Request

FIG. 14 shows an RR process of the B BPL during the A BPL monitoringwhen the RR is performed upon the BPL quality reporting request of thebase station, when the two BPLs are monitored, and when the SS block(i.e., composite beam) is used for the new beam identification purpose.If the base station triggers the quality reporting to the terminalthrough the BPL on one of the RRC/DCI/MAC-CE at operation 1410, theterminal may transmit the RSRP information (which is to include thefailure information on the B BPL) for the A/B BPL and the informationfor the preferred composite beam at operation 1420. Alternatively, theID that can be distinguished for the A/B BPL can be used to transmit theinformation on the ID of the BPL, the RSRP of BPL, and the preferredcomposite beam. The information on the preferred composite beam meansthat the selected beam ID or the port ID based on the SS block may referto the resource ID. The reason for transmitting the same is to allow theterminal to choose a new fine BPL for updating the failure occurrenceBPL (B BPL) (i.e., to refine the beam selected based on the SS block).It is also possible to transmit a plurality of preferred composite beaminformation from the terminal to the base station. In this case, it ishelpful to find whether there is better BPL for the A BPL whilereviewing the alternative beam for the B BPL in which the failureoccurs.

The base station may activate and transmit the CSI-RS using one of theRRC/DCI/MAC-CE based on the information on the composite beam(s)transmitted by the terminal at operation 1430, and the terminal maytransmit the alternative BPL information for changing the failure BPL (BBPL) through one of the UCI/MAC-CE at operation 1450 based on the CSI-RSreceiving value at operation 1440. Alternatively, the alternative BPLinformation for changing the failure BPL (B BPL) and the BPL informationfor updating the A BPL may be included. At this time, the alternativeBPL for the B BPL may be A BPL. The base station receiving theinformation may rearrange the monitoring order for the A BPL and thereporting BPL received from the terminal through one of theRRC/DCI/MAC-CE at operation 1460. Alternatively, the terminal may informthe terminal of the alternate BPL information for changing the failureBPL (B BPL) and the A BPL through one of the RRC/UCI/MAC-CE. That is, atthis time, the A/B BPL is replaced by the C/D BPL. The monitoring orderof the C/D BPL may be notified to the terminal through one of theRRC/DCI/MAC-CE. At this time, the monitoring period of the C/D may bekept the same as the monitoring period of A/B. Alternatively, ifnecessary, the base station may change the monitoring period of themonitoring BPLs to the terminal through one of the RRC/DCI/MAC-CE.

According to another embodiment, when instead of the SS block, theCSI-RS is used for the new beam identification, the terminal may reportthe beam/port/resource ID for replacing B or A/B selected based on theCSI-RS, not the beam/port/resource ID selected based on the SS blockupon the quality reporting for the monitoring BPLs. In this case, afterreceiving the BPL information reported to the terminal, the base stationmay perform the alternative BPL confirmation, the order re-establishedor the like for the B or the A/B BPL through one of the RRC/MAC-CE/DCI.

According to another embodiment, when the SS block is used for new beamidentification, as in the embodiment illustrated in FIG. 13, theterminal may report the beam/port/resource ID for replacing B or A/Bselected based on the SS block at the time of the quality reporting forthe monitoring BPLs, and then immediately re-establish the alternativeconfirmation and the order for B or A/B BPL through one of theRRC/MAC-CE/DCI without performing the fine beam association processthrough the CSI-RS transmission. After the recovery procedure, the basestation may further perform the refinement for the updated monitoringBPLs if necessary.

Beam Failure Recovery Using PRACH-Like Channel (PRACH-Like RR Region)

FIG. 15 shows a first embodiment of the PRACH-like RR region utilizationRR process for the B BPL during the A BPL monitoring when two BPLs aremonitored and the PRACH-like channel is associated with SS blocks. Theterminal transmits the RR message in the PRACH-like RR region atoperation 1510. Thereafter, any BPL of the A/B BPL may transmit thealternative BPL information together with the information of the failureoccurrence BPL through one of the UCI/MAC-CE at operation 1540.Alternatively, if both A/B BPL failures occur, the alternative BPLs forboth BPLs may be reported. The alternative BPL information may include aresource/beam/port ID associated with the CSI-RS transmitted by the basestation after the terminal recovery request. The CSI-RS transmitted bythe base station after the terminal recovery request may be associatedwith the recovery request selection resource of the terminal. Forexample, if the terminal performs the RR through the PRACH-like RRresource associated with SS block #1, the base station may download, tothe terminal, the fine beam in the direction associated with the SSblock #1 beam direction. However, this is not limited to a standard as abase station implementation. Therefore, the base station may transmitthe beam (or BPL) ID and monitoring order information for the alternateBPL(s) through one of the RRC/DCI/MAC-CE at operation 1550.

According to another embodiment, if the PRACH-like channel is associatedwith the SS block and the CSI-RS, the terminal may determine whether totransmit the CSI-RS for the refinement depending on whether to performthe recovery request in the PRACH-like resource associated with the SSblock or whether to perform the recovery request in the PRACH-likeresource associated with the CSI-RS. For example, if the terminalperforms the recovery request in the PRACH-like resource associated withthe SS block, the base station may activate the CSI-RS for the terminalto find the fine beam to replace the failure occurrence BPL.

FIG. 16 shows a second embodiment of the RR region utilization RRprocess for the B BPL during the A BPL monitoring when two BPLs aremonitored and the PRACH-like channel is associated with SS blocks. Whentransmitting the RR in the PRACH-like RR region, the terminal transmitsinformation on whether the failure occurrence BPL is A or B. This can bedivided into resources (frequency/time/sequence, or the like).Alternatively, the terminal may transmit a situation in which all of theA/B BPLs have failed upon transmitting the RR message. In thisembodiment, the terminal can report the information on the BPL(s) toreplace the failed BPL(s) through the UCI/MAC-CE. Therefore, the basestation may transmit one of the beam (or BPL) ID and monitoring orderinformation for the alternate BPL(s) through one of the RRC/DCI/MAC-CE.

According to another embodiment, even when the PRACH-like channel isassociated with the SS block and the CSI-RS, the information on whetherthe failure occurrence beam is A or B can be transmitted through therecovery request. This can be divided into resources(frequency/time/sequence, or the like). Alternatively, the terminal maytransmit a situation in which all of the A/B BPLs have failed upontransmitting the RR message. The resource in which the terminaltransmits the RR may indicate the alternative beam information on thefailure generation beam, and if the alternative beam for the failureoccurrence beam is the beam associated with the SS block (i.e., thefailure situation of the specific BPL is reported in the PRACH-likechannel associated with the SS block), the base station may activate theCSI-RS to perform the refinement for the corresponding BPL together.

Beam Failure Recovery when Terminal Performs Subjective RR

FIG. 17 shows an embodiment of the operation of the base station and theterminal operation when terminal-subjective RR is performed. Inparticular, FIG. 17 shows the case of performing the RR for the B BPLduring the A BPL connection. As shown in FIG. 17, the terminal canperform the RR on the failure occurrence BPL in the UL resourceallocated through the grant after the SR request through the periodicPUCCH. Alternatively, the terminal may immediately transmit an RRrequest message (including failure BPL and alternative BPL information)on the PUCCH.

Beam Failure Recovery According to New Beam Identification RS

If the SS block and the CSI-RS are used for the new beam identificationRS, the (beam indication) corresponding information should include thefollowing information when the terminal reports the alternative BPLinformation for the failure BPL to the base station

-   -   1) Whether the alternative BPL for the failure BPL is associated        with the CSI-RS or is associated with the SS block    -   2) Based on the above 1), whether the alternative BPL for the        failure BPL is any resource/beam/port ID

For example, if the terminal finds the alternative BPL for the failureBPL in the already configured CSI-RS from the base station, the terminaltransmits the BPL found by the beam based on the CSI-RS and theresource/beam/port ID information of the CSI-RS in order to inform thebase station of the alternative BPL.

Beam Failure Recovery According to Beam Failure Recovery RequestTriggering Condition

If a beam failure RR triggering condition is defined in the condition 3of the above-described beam failure RR triggering condition, theterminal transmits the failure occurrence information and the BPLinformation replacing the respective failure occurrence BPL when thefailure for one or more of the monitoring BPLs occurs. At this time, thealternative BPL for each failure occurrence BPL may be the same as theBPL in which no failure occurred during the current monitoring BPLs. Atthis time, the alternative BPL information for the failure occurrenceBPL

-   -   1) may be the CSI-RS configured in the terminal and the        resource/beam/port ID based on the SS block, and    -   2) may be the CSI-RS configured in the terminal or the        resource/beam/port ID based on the SS block or the ID of the BPL        (e.g., the A/B BPL is monitored before the terminal performs the        RR and indicates the ID when the ID is designated by A No. 1 and        B No. 2 among the monitoring BPLs) in which the failure does not        occurs among the monitoring BPLs.

That is, in the case of a system applying the above 2), the alternativeBPL information for each failure occurrence BPL should include thefollowing information: information for dividing the CSI-RI or SSblock-based ID or the monitoring BPL ID and information on how many IDsthe divided ID belongs to.

If the beam failure RR triggering condition is defined in the condition2 of the above-described beam failure RR triggering condition, the UEdoes not necessarily report the alternative BPL information for thefailure occurrence BPL to the base station or notify that there is noalternative BPL for the occurrence BPL. FIG. 18 shows an embodiment inwhich when the terminal performs the mode 1, if the beam failure RRtriggering condition 2 is applied to the system, the RACH using thePRACH-like RR region utilization RR for the A/B BPL is performed duringthe A BPL connection. The terminal notifies the base station that thefailure occurs for the specific BPL but there is no alternative beam forthe corresponding failure occurrence BPL. Therefore, the base stationselects one of the monitoring BPLs before the terminal performs therecovery request as the BPL information for the respective failureoccurrence BPL through one of the RRC/MAC-CE/DCI.

Alternatively, in the above embodiment, when the system defines the beamfailure RR triggering condition in the condition 2 of the beam failureRR triggering condition and only two BPLs are monitored, if the terminalnotifies the base station that there is no alternative beam for the BPLin which the failure occurs, the base station and the terminal may beautomatically connected to each other by the BPL, in which the failuredoes not occur, in the interval in which the base station and theterminal are connected to each other by the failure occurrence BPL

The above operation is applicable even when the PRACH-like RR resourceis not utilized.

In the above embodiments, the overall beam recovery procedure isperformed by the BPL corresponding to the PRACH-like RR resource inwhich the terminal transmits the recovery request. However, in the casein which the BPL information is immediately transmitted to thePRACH-like RR resource and two BPLs are monitored, the DL/UL between thebase station and the terminal may be made from the response of the basestation for the RR by the BPL in which the failure does not occurs (FIG.19).

DL/UL Beam Designation

In the case of monitoring the multi-BPL, if the base station transmitsthe DCI to a DL transmission beam corresponding to a specific BPL amongthe BPLs included in the multi-BPL, the terminal should transmit the UCIand UL to the UL transmission beam corresponding thereto (correspondingto the same BPL). Alternatively, if the base station transmits the DCIby the DL transmission beam corresponding to the specific BPL, theterminal may instruct the DCI to transmit the UCI and UL data by the ULtransmission beam (corresponding to another BPL which is beingmonitored) which does not correspond thereto. Here, the UL transmissionbeam corresponding to the beam for transmitting the DCI is notnecessarily the same direction/width as the reception beam used by theterminal to receive the corresponding DCI, and the UL transmission beamsfor the UCI and UL data also may be the same as or different from eachother.

Alternatively, for the DCI transmitted by the specific DL beam, theterminal may not necessarily transmit the UCI and UL data to the ULtransmission beam corresponding thereto. For example, in HARQ bundlingof the DL data scheduled from the DCI of the plurality of monitoringBPLs, it is possible to perform UL through the BPL connected at a batchHARQ transmission time for the DCIs transmitted in different DL BPLs.

Alternatively, the system may perform HARQ bundling only on the DL datascheduled by the DCI transmitted in the same BPL.

Alternatively, in the multi-BPL monitoring situation, the system may notexecute commands requiring batch processing for multi-DCI.

The base station may configure the one CORSET allocated to the terminalto have the QCL relationship with N CSI-RS resources. Alternatively, thebase station may allocate, to the terminal, N CORSETs which are QCLedwith one CSI-RS resource.

The terminal finds optimal reception beams for each of N CSI-RSresources to form the BPL, measures the RSRP values of the CSI-RSresource based on the BPLs formed for each CSI-RS resource, therebydetermining the beam failure detection. Meanwhile, the RSRP value may bereplaced by the SINR value or the RSRQ value and then applied.

The recovery request signal may be generated by combining two resources.The first resource configuring the recovery request signal may includeinformation indicating whether the terminal detects the beam failure bymeasuring any of the N CSI-RS resources. The second resource configuringthe recovery request signal may include information indicating theresource index of the SS-block or the resource index of the CSI-RS inwhich the terminal has identified the new candidate beam.

Hereinafter, to describe the embodiment, it is assumed that N=2, and theN CSI-RS resources each are defined as “A” and “B”.

The first resource may indicate the information on whether the beamfailure has been detected at “A”, whether the beam failure has beendetected at “B”, or whether the beam failure has been detected at both“A” and “B”. For example, for the first resource, the base station mayallocate three different sequences S1, S2, and S3 to the terminal. Ifthe terminal detects the beam failure only for “A”, the terminal may usethe first sequence S1 when transmitting the recovery request signal. Ifthe terminal detects the beam failure only for “B”, the terminal may usethe second sequence S1 when transmitting the recovery request signal. Ifthe terminal detects the beam failure only for “A” and “B”, the terminalmay use the third sequence S3 when transmitting the recovery requestsignal.

When the number of SS-block indexes that may be used for new beamidentification is defined as T (for example, T=64), the second resourcemay consist of T+1. At this time, each resource may be defined by X0,X1, . . . , XT. If there is no new candidate beam newly identified bythe terminal, the terminal may transmit the recovery request byselecting the resource X0. If the terminal identifies a new candidatebeam by measuring the SS-block corresponding to SS-block index t, theterminal may transmit the recovery request using resource XT. The secondresource may be defined by T+1 by dividing the time/frequency resource.

In the above embodiment, when the S1 sequence corresponding to the beamfailure of the “A” resource is used for the recovery requesttransmission and the time/frequency resource location corresponding toX0 is used, it may be assumed that the terminal transmits the responseof the base station for the recovery request to the CORSET that is QCLedto the “B” resource. After the predetermined time from a predeterminedtime when the terminal transmits the recovery request, the terminal mayperform the monitoring on the CORSET to receive the response. Theterminal may find the information on whether the configuration for theCORSET QCLed for the existing “A” resource is changed to the QCL for the“B” resource by receiving the response.

In the above embodiment, when the S1 sequence corresponding to the beamfailure of the “A” resource is used for the recovery requesttransmission and the time/frequency resource location corresponding toX0 is used, it may be assumed that the terminal transmits the responseof the base station for the recovery request to the CORSET that is QCLedto the “B” resource. After the predetermined time from a predeterminedtime when the terminal transmits the recovery request, the terminal mayperform the monitoring on the CORSET to receive the response. Theterminal may find the information on whether the configuration for theCORSET QCLed for the existing “B” resource is changed to the QCL for the“A” resource by receiving the response.

In the above embodiment, when the S3 sequence corresponding to the beamfailure of both of the “A” and “B” resources is used for the recoveryrequest transmission and the time/frequency resource locationcorresponding to XT is used, it may be assumed that the terminaltransmits the response of the base station for the recovery request tothe CORSET that is QCLed to the SS-block index t. After thepredetermined time from a predetermined time when the terminal transmitsthe recovery request, the terminal may perform the monitoring on theCORSET to receive the response. The terminal may find the information onwhether the configuration for the CORSET QCLed for the existing “A” and“B” resources is changed to the QCL for the SS-block index t byreceiving the response.

In the above embodiment, when the S1 sequence corresponding to the beamfailure of the “A” resource is used for the recovery requesttransmission and the time/frequency resource location corresponding toXT is used, it may be assumed that the terminal transmits the responseof the base station for the recovery request to the CORSET that is QCLedto the SS-block index t. After the predetermined time from apredetermined time when the terminal transmits the recovery request, theterminal may perform the monitoring on the CORSET to receive theresponse. The terminal may find the information on whether theconfiguration for the CORSET QCLed for the existing “A” resource ischanged to the QCL for the SS-block index t or is changed to the QCL forthe “B” resource by receiving the response.

In the above embodiment, when the S2 sequence corresponding to the beamfailure of the “B” resource is used for the recovery requesttransmission and the time/frequency resource location corresponding toXT is used, it may be assumed that the terminal transmits the responseof the base station for the recovery request to the CORSET that is QCLedto the SS-block index t. After the predetermined time from apredetermined time when the terminal transmits the recovery request, theterminal may perform the monitoring on the CORSET to receive theresponse. The terminal may find the information on whether theconfiguration for the CORSET QCLed for the existing “B” resource ischanged to the QCL for the SS-block index t or is changed to the QCL forthe “A” resource by receiving the response.

FIG. 20 is a block diagram of a base station according to an embodimentof the disclosure.

Referring to FIG. 20, a base station includes a base station processor(2010), a base station receiver (2020) and a base station transmitter(2030). The base station processor (2010) may refer to a controller, acircuitry, an application-specific integrated circuit (ASIC), or atleast one processor configured to perform the operations of the basestation illustrated in the figures, e.g., FIGS. 1 to 19, or describedabove. The base station receiver (2020) and the base station transmitter(2030) are functionally coupled with the base station processor (2010)to allow the base station to communicate with other entity such as aterminal.

For example, the base station transmitter (2030) is configured totransmit a signal to a terminal. The base station processor (2010) maybe configured to identify reference signals for measuring a plurality ofbeams and control the base station transmitter (2030) to transmitinformation on the reference signals to the terminal by higher layer(e.g., RRC) signaling. The information on the reference signals mayindicate which type of the reference signals is used for measuring theplurality of beams. For example, the information on the referencesignals indicates whether the terminal measures the plurality of beamsby using SS blocks, CSI-RSs, or both the SS blocks and the CSI-RSs. Inaddition, the base station processor (2010) may determine a thresholdfor measuring the plurality of beams based on a type of the referencesignals, and control the base station transmitter (2030) to transmitinformation on the threshold to the terminal by higher layer (e.g., RRC)signaling. The base station processor (2010) may determine the thresholdfor SS blocks to be different from the threshold for CSI-RSs.

FIG. 21 is a block diagram of a terminal according to an embodiment ofthe disclosure.

Referring to FIG. 21, a terminal includes a terminal processor (2110), aterminal receiver (2120) and a terminal transmitter (2130). The terminalprocessor (2110) may refer to a controller, a circuitry, an ASIC, or atleast one processor configured to perform the operations of a terminalillustrated in the figures, e.g., FIGS. 1 to 19, or described above. Theterminal receiver (2120) and the terminal transmitter (2130) arefunctionally coupled with the terminal processor (2110) to allow theterminal to communicate with other entity such as a base station.

For example, the terminal receiver (2120) is configured to receive asignal from a base station. The terminal processor (2110) may beconfigured to control the terminal receiver (2120) to receiveinformation on a reference signal from the base station by higher layer(e.g., RRC) signaling, measure a plurality beams based on theinformation on the reference signal, and determine at least onecandidate beam among the plurality beams. The candidate beam comprises abeam quality above a threshold. The information on the reference signalmay indicate which type of reference signals are used for measuring theplurality of beams. For example, the information on the reference signalindicates whether to measure the plurality of beams by using SS blocks,CSI-RSs, or both the SS blocks and the CSI-RSs. In addition, theterminal processor (2110) may control the terminal receiver (2120) toreceive information on the threshold from the base station by higherlayer (e.g., RRC) signaling. The threshold is associated with a type ofthe reference signal for measuring the plurality of beams. Specifically,the threshold for SS blocks may be different from the threshold forCSI-RSs.

While the disclosure has been shown and described with reference tovarious embodiments thereof, it will be understood by those skilled inthe art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the disclosure as definedby the appended claims and their equivalents.

Although the present disclosure has been described with variousembodiments, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

What is claimed is:
 1. A method performed by a terminal for beam failurerecovery in a wireless communication system, the method comprising:receiving, from a base station, configuration information includinginformation on first reference signals identifying candidate beams forbeam failure recovery and information on a threshold for determiningwhether a candidate beam is used for the beam failure recovery;measuring at least one second reference signal for detecting beamfailure; in case that the beam failure is detected, identifying a thirdreference signal with reference signal received power (RSRP) above thethreshold among the first reference signals; and transmitting, to thebase station, a beam failure recovery request based on the thirdreference signal.
 2. The method of claim 1, wherein the first referencesignals include at least one of a channel state information-referencesignal (CSI-RS) or a synchronization signal (SS) block.
 3. The method ofclaim 2, wherein the threshold associated with the CSI-RS is configuredto have a different value from the threshold associated with the SSblock.
 4. The method of claim 1, wherein the configuration informationfurther includes a list of the at least one second reference signal. 5.The method of claim 1, wherein the at least one second reference signalincludes at least one of a channel state information-reference signal(CSI-RS) or a synchronization signal (SS) block.
 6. A method performedby a base station for beam failure recovery in a wireless communicationsystem, the method comprising: transmitting, to a terminal,configuration information including information on first referencesignals identifying candidate beams for beam failure recovery andinformation on a threshold for determining whether a candidate beam isused for the beam failure recovery; transmitting, to the terminal, atleast one second reference signal for detecting beam failure; and incase that the beam failure is detected based on the at least one secondreference signal, receiving, from the terminal, a beam failure recoveryrequest based on a third reference signal with reference signal receivedpower (RSRP) above the threshold among the first reference signals. 7.The method of claim 6, wherein the first reference signals include atleast one of a channel state information-reference signal (CSI-RS) or asynchronization signal (SS) block.
 8. The method of claim 7, wherein thethreshold associated with the CSI-RS is configured to have a differentvalue from the threshold associated with the SS block.
 9. The method ofclaim 6, wherein the configuration information further includes a listof the at least one second reference signal.
 10. The method of claim 6,wherein the at least one second reference signal includes at least oneof a channel state information-reference signal (CSI-RS) or asynchronization signal (SS) block.
 11. A terminal in a wirelesscommunication system, the terminal comprising: a transceiver; and atleast one processor coupled with the transceiver and configured to:receive, from a base station via the transceiver, configurationinformation including information on first reference signals identifyingcandidate beams for beam failure recovery and information on a thresholdfor determining whether a candidate beam is used for the beam failurerecovery, measure at least one second reference signal for detectingbeam failure, in case that the beam failure is detected, identify athird reference signal with reference signal received power (RSRP) abovethe threshold among the first reference signals, and transmit, to thebase station via the transceiver, a beam failure recovery request basedon the third reference signal.
 12. The terminal of claim 11, wherein thefirst reference signals include at least one of a channel stateinformation-reference signal (CSI-RS) or a synchronization signal (SS)block.
 13. The terminal of claim 12, wherein the threshold associatedwith the CSI-RS is configured to have a different value from thethreshold associated with the SS block.
 14. The terminal of claim 11,wherein the configuration information further includes a list of the atleast one second reference signal.
 15. The terminal of claim 11, whereinthe at least one second reference signal includes at least one of achannel state information-reference signal (CSI-RS) or a synchronizationsignal (SS) block.
 16. A base station in a wireless communicationsystem, the base station comprising: a transceiver; and at least oneprocessor coupled with the transceiver and configured to: transmit, to aterminal via the transceiver, configuration information includinginformation on first reference signals identifying candidate beams forbeam failure recovery and information on a threshold for determiningwhether a candidate beam is used for the beam failure recovery,transmit, to the terminal via the transceiver, at least one secondreference signal for detecting beam failure, and in case that the beamfailure is detected based on the at least one second reference signal,receive, from the terminal via the transceiver, a beam failure recoveryrequest based on a third reference signal with reference signal receivedpower (RSRP) above the threshold among the first reference signals. 17.The base station of claim 16, wherein the first reference signalsinclude at least one of a channel state information-reference signal(CSI-RS) or a synchronization signal (SS) block.
 18. The base station ofclaim 17, wherein the threshold associated with the CSI-RS is configuredto have a different value from the threshold associated with the SSblock.
 19. The base station of claim 16, wherein the configurationinformation further includes a list of the at least one second referencesignal.
 20. The base station of claim 16, wherein the at least onesecond reference signal includes at least one of a channel stateinformation-reference signal (CSI-RS) or a synchronization signal (SS)block.